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The Search for a White Worm

Like most postdocs who have just walked away from six (or more) years of life as a graduate student, I moved to a new college town, to a new lab, and to a new model system. I saw this as my opportunity to learn new techniques and to answer those unknown questions about regeneration, but like many young scientists, I did not want to go after the low hanging fruit. I chatted with my new PI about potential research projects and chose what I thought was a novel and innovative project. At the same time, I was training to run a marathon. I probably should have realized what to expect over the next three years when he told me, “Training for this marathon is going to be so easy compared to the project you’ve undertaken.”

I recently published in Nature the results of this project, the identification of aberrant Wnt signaling as the cause of limited regeneration ability in a flatworm species, and surprisingly the ability to rescue regeneration by manipulating a single gene. It answered a centuries old question; it was not low hanging fruit; and my PI was right—the path to get there was at times more challenging than running my first marathon, but in ways I never anticipated.

Adult Procotyla worm.

From middle school science class, most of us remember the extraordinary regeneration abilities of planarians. Chop off a worm’s head, and it regrows in a matter of days! Yet some species lack such a robust regenerative ability and cannot regrow heads after amputation in the posterior half of their bodies. This was to be my project—to investigate how evolution has tinkered with these planarians to limit regeneration. While over 100 species of planarians have been described to have such lackluster regeneration abilities, only one species inhabits streams in North America. Shortly after arriving in my postdoc lab, it was time to find this one small white worm called Procotyla. According to the catalogs, all the biological supply companies (Carolina, Wards, and the like) stock them, but much to my chagrin I quickly realized they were in the business of selling any white planarian they could find and not interested in proper taxonomic identification.

Step one of my postdoctoral research project, finding the flatworm with broken regeneration, had just become more difficult. My inner field ecologist was bursting with excitement as I left the lab in search of streams that harbored Procotyla. Sadly, Procotyla was not in streams on campus, nor was it in any of the nearby streams and rivers I visited. Sure, I found hundreds of planarians—brown ones, black, ones, gray ones, but never a white one. My PI remembered having seen Procotyla in Maryland when he was a postdoc so I flew to the East Coast and scoured streams all over the mid-Atlantic states only to return to the Midwest empty handed. At this point, months into my postdoc, I had spent more time flipping rocks in streams than I had holding a pipette at my lab bench.

Success came after combing through the online Smithsonian flatworm collection to identify two streams in southern Illinois where these worms had been collected 50 years previously. Using Google Maps I plotted the location of these streams, not paying particular attention to the fact that the winding dirt road leading to this area was called Snake Road. After applying for the necessary permits from a handful of government agencies and driving four hours, a graduate student and I arrived at Snake Road to find it closed to vehicular traffic due to the biannual snake migration. Yes, the only two streams where I could manage to find the regeneration-deficient planarian were located along one of the most famous snake migration routes east of the Mississippi River.

Park rangers warned us about one particular species of pit viper called a water moccasin which I later learned via Wikipedia is highly aggressive and the only semiaquatic poisonous snake in the United States. While I am not particularly afraid of snakes, this one species put me on edge and sure enough while I sat in a stream flipping rock after rock looking for a white worm beneath it, the stick next to my left leg began to move. Luckily, this snake was not as aggressive as the Internet made them out to be, and I escaped without being bitten. The danger of snakes lurking around every corner was accompanied by swarming mosquitos, humid conditions, and bloodthirsty ticks routinely crawling up our legs.

The streams along Snake Road produced a bounty of Procotyla, but I quickly realized that Procotyla does not live happily or reproduce in the laboratory. Over the course of the next three years, I recruited members of the lab to accompany me on more than eight collection trips. We turned over thousands of rocks looking for that white dot of a worm adhering to their underside and managed to collect enough animals to complete the experiments that appear in Nature this month. Unlike most young scientists who are lucky enough to publish in Nature, I was not most challenged by spending hours and hours in the lab or difficult protocols that never seem to work. Traversing hundreds of streams in the eastern half of the United States and battling poisonous snakes and blood sucking insects to find an elusive white worm in southern Illinois streams was the first stage of my postdoctoral experience that helped answer a long-standing question in regeneration biology.